1. Field of the Invention
The present invention relates to a hub nut with a washer and which is designed to prevent the slipping out or loss of the washer.
2. Description of the Prior Art
The hub nut is a hub-tightening means for an automobile wheel. Conventionally, the nut and the washer are separately provided, but they are troublesome for assembling, and the washer is therefore liable to be lost. For these reasons, recently a hub nut with a washer non-slippably attached thereto has come to be used often.
Hub nuts of this kind are disclosed in the Japanese Utility Model Application Nos. Sho 50-46269 (Laying-open No. Sho 51-124573) and Sho 47-98059 (Publication No. Sho 50-43641). According to the manner in which the washer is attached to the nut, that may be broadly classified as the "shrink-fit" type, the "caulking" type and the "press-fit" type, but they have the following drawbacks.
In the shrink-fit type, a cylindrical part is projectingly formed on the nut base, and on the outer surface of the cylindrical part is cut an annular groove. A washer, with an inner diameter smaller than the outer diameter of the cylindrical part and larger than the outer diameter of the annular groove, is heated enough to make the inner diameter thereof larger than the outer diameter of the cylindrical part, and the washer in its heated state is fitted into the groove and thereafter cooled to the ambient temperature, thereby preventing the washer from slipping out of the nut. This type, however, has drawbacks in that the outer diameter of the cylindrical part and the inner diameter of the washer have to be highly accurate and heating is needed for fitting the washer.
In the caulking type, a cylindrical part is projectingly formed on the nut base, and on the outer surface of the cylindrical part an annular groove is cut. A washer, with an inner diameter larger than the outer diameter of the cylindrical part is fitted into the groove and, in this state, the washer is caulked at several spots inwards in the radial direction, thereby forming a radially inwardly projecting part. This projecting part is extended into the groove, thus preventing the washer from slipping out of the nut. This type, however, has drawbacks in that the grooves in the outer diameter of the cylindrical part must be provided by cutting, and when the caulked projecting part is too large, the washer refuses to turn therein.
In the press-fit type, a cylindrical part is projectingly formed on the nut base, and a tapered projecting part is formed on the outside of the cylindrical part at a position separated by the width of the washer from the nut base such that the diameter may gradually increase in the direction of fitting the washer. An annular groove, with an outer diameter smaller than the outer diameter of the cylindrical part, is formed on the cylindrical part between the projecting part and the nut base, and a washer, with an inner diameter larger than the outer diameter of the groove and smaller than the outer diameter of the tapered projecting part, is press-fitted over the tapered projecting part into the groove of the nut, thereby preventing the washer from slipping out of the nut. This type, however, has drawbacks in that the cylindrical part, the tapered projecting part and the annular groove must be provided by cutting, and the portion of the tapered projecting part which interferes with the disc wheel to be fitted with a nut to be beveled, thereby increasing the work steps. Such beveling also is likely to increase the surface pressure of the light alloy disc wheel, thereby causing slackness.